Considering sex as a biological variable in modern digital health solutions, we investigated sex-specific differences in the trajectory of four physiological parameters across a COVID-19 infection. A wearable medical device measured breathing rate, heart rate, heart rate variability, and wrist skin temperature in 1163 participants (mean age = 44.1 years, standard deviation [SD] = 5.6; 667 [57%] females). Participants reported daily symptoms and confounders in a complementary app. A machine learning algorithm retrospectively ingested daily biophysical parameters to detect COVID-19 infections. COVID-19 serology samples were collected from all participants at baseline and follow-up. We analysed potential sex-specific differences in physiology and antibody titres using multilevel modelling and t-tests. Over 1.5 million hours of physiological data were recorded. During the symptomatic period of infection, men demonstrated larger increases in skin temperature, breathing rate, and heart rate as well as larger decreases in heart rate variability than women. The COVID-19 infection detection algorithm performed similarly well for men and women. Our study belongs to the first research to provide evidence for differential physiological responses to COVID-19 between females and males, highlighting the potential of wearable technology to inform future precision medicine approaches.

Background During and after mild (no hospitalization) or moderate (hospitalization without ICU) SARS-CoV-2 infections, a wide range of symptoms, including neurological disorders have been reported. It is, however, unknown if these neurological symptoms are associated with brain injury and whether brain injury and related symptoms also emerge in patients suffering from Long-COVID. Neuronal biomarkers such as serum neurofilament light chain and glial fibrillary acidic protein can be used to elucidate neuro-axonal and astroglial injuries. We therefore investigated whether these biomarkers are associated with the COVID-19 infection status (mild-to-moderate), the associated symptoms and Long-COVID. Methods From 146 individuals of the general population with a post-acute, mild-to-moderate SARS-CoV-2 infection, serum neurofilament light chain (sNfL; marker of intra-axonal neuronal injury) and serum glial fibrillary acidic protein (sGFAP; marker of astrocytic activation/injury) were measured. Samples were taken before, during and after (five and ten months) a SARS-CoV-2 infection. Individual symptoms and Long-COVID status were assessed using questionnaires. Results Neurological symptoms were described for individuals after a mild and moderate COVID-19 infection, however, serum markers of brain injury (sNfL/sGFAP) did not change after an infection (sNfL: P = 0.74; sGFAP: P = 0.24) and were not associated with headache ( P = 0.51), fatigue ( P = 0.93), anosmia ( P = 0.77) and ageusia ( P = 0.47). In participants with Long-COVID, sGFAP ( P = 0.038), but not sNfL ( P = 0.58) significantly increased but was not associated with neurological symptoms. Conclusion Neurological symptoms in individuals after a mild-to-moderate SARS-CoV-2 infection with and without Long-COVID were not associated with brain injury, although there was some astroglial injury observed in Long-COVID patients. Funding The COVI-GAPP study received grants from the Innovative Medicines Initiative (IMI grant agreement number 101005177), the Princely House of Liechtenstein, the government of the Principality of Liechtenstein, and the Hanela Foundation (Switzerland). None of the funders played a role in the study design, data collection, data analysis, data interpretation, writing of the report, or decision to publish.

It is unknown whether neurological symptoms are associated with brain injury after SARS-CoV-2 infections and whether brain injury and related symptoms also emerge in Long-COVID patients. Biomarkers such as serum neurofilament light chain (sNfL) and glial fibrillary acidic protein (sGFAP) can be used to elucidate neuro-axonal and astroglial injuries. We investigated whether these biomarkers are associated with COVID-19 infection status, associated symptoms and Long-COVID. From 146 individuals of the general population with a post-acute, mild-to-moderate SARS-CoV-2 infection, sNfL and sGFAP were measured before, during and after (five and ten months) the infection. Individual symptoms and Long-COVID status were assessed using questionnaires. Neurological associated symptoms were described for individuals after a mild and moderate COVID-19 infection; however, sNfL (p = 0.74) and sGFAP (p = 0.24) did not change and were not associated with headache (p = 0.51), fatigue (p = 0.93), anosmia (p = 0.77) or ageusia (p = 0.47). In Long-COVID patients, sGFAP (p = 0.038), but not sNfL (p = 0.58), significantly increased but was not associated with neurological associated symptoms. Long-COVID status, but not post-acute SARS-CoV-2 infections, may be associated with astroglial injury/activation, even if neurological associated symptoms were not correlated.

OBJECTIVES:We investigated machinelearningbased identification of presymptomatic COVID-19 and detection of infection-related changes in physiology using a wearable device.DESIGN:Interim analysis of a prospective cohort study.SETTING, PARTICIPANTS AND INTERVENTIONS:Participants from a national cohort study in Liechtenstein were included. Nightly they wore the Ava-bracelet that measured respiratory rate (RR), heart rate (HR), HR variability (HRV), wrist-skin temperature (WST) and skin perfusion. SARS-CoV-2 infection was diagnosed by molecular and/or serological assays.RESULTS:A total of 1.5 million hours of physiological data were recorded from 1163 participants (mean age 44±5.5 years). COVID-19 was confirmed in 127 participants of which, 66 (52%) had worn their device from baseline to symptom onset (SO) and were included in this analysis. Multi-level modelling revealed significant changes in five (RR, HR, HRV, HRV ratio and WST) device-measured physiological parameters during the incubation, presymptomatic, symptomatic and recovery periods of COVID-19 compared with baseline. The training set represented an 8-day long instance extracted from day 10 to day 2 before SO. The training set consisted of 40 days measurements from 66 participants. Based on a random split, the test set included 30% of participants and 70% were selected for the training set. The developed long short-term memory (LSTM) based recurrent neural network (RNN) algorithm had a recall (sensitivity) of 0.73 in the training set and 0.68 in the testing set when detecting COVID-19 up to 2 days prior to SO.CONCLUSION:Wearable sensor technology can enable COVID-19 detection during the presymptomatic period. Our proposed RNN algorithm identified 68% of COVID-19 positive participants 2 days prior to SO and will be further trained and validated in a randomised, single-blinded, two-period, two-sequence crossover trial. Trial registration number ISRCTN51255782; Pre-results.

Background: We investigated machine learning based identification of the pre-symptomatic coronavirus disease 2019 (COVID-19) and detection of infection-related changes in physiology using a wearable device (the Ava bracelet). Methods: Participants from an ongoing cohort study (GAPP) of the general population in Liechtenstein were included in the current sub-study (COVI-GAPP). Nightly they wore the fertility bracelet that measured every ten seconds skin temperature, heart rate, respiratory rate, skin perfusion, and heart rate variability. Participants reported daily symptoms in a complementary app. Laboratory reverse transcription polymerase chain reaction (RT-PCR) and/or COVID-19 serology samples were collected from all participants. Long short-term memory (LSTM) based recurrent neural networks (RNN) were chosen for the binary classification of an individual as healthy or infected on a given day in a derivation and validation procedure. Findings: A total of 1ž5 million hours of physiological data were recorded from 1163 participants (mean age 44 +/- 5ž5 years). COVID-19 was confirmed in 127 participants. Of these, 66 (52%) had worn their device from baseline to symptom onset and were included in the analysis and RNN. Multi-level modelling revealed significantly different values in pre- versus post-symptomatic respiratory rate, temperature, heart rate, heart rate variability ratio, and skin perfusion. The developed RNN algorithm had a recall of 0ž73 in the training set and 0ž68 in the testing set (overall recall of 0ž71) when detecting COVID-19 up to two days prior to symptom onset. Interpretation: Our proposed RNN algorithm identified 71% of COVID-19 positive participants two days prior to symptom onset. Wearable sensor technology can therefore enable COVID-19’ detection during the pre-symptomatic period. Funding: IMI grant agreement number 101005177, the Princely House of the Principality of Liechtenstein, the government of the Principality of Liechtenstein, and the Hanela Foundation in Switzerland. Declaration of Interest: Lorenz Risch, and Martin Risch are key shareholders of the Dr Risch Medical Laboratory. David Conen has received consulting fees from Roche Diagnostics, outside of the current work. The other authors have no financial or personal conflicts of interest to declare. Ethical Approval: The local ethics committee approved the study protocol, and written informed consent was obtained from each participant (BASEC 2020-00786).

Although SARS-CoV-2 antibody assays have been found to provide valid results in EDTA-anticoagulated whole blood, so far, they have not demonstrated that antibody levels in whole blood originating from capillary blood samples are comparable to antibody levels measured in blood from a venous origin. Here, blood is drawn simultaneously by capillary and venous blood sampling. Antibody titers are determined by an assay employing electrochemiluminescence (ECLIA) and SARS-CoV-2 total immunoglobulins are detected with specificity directed against the nucleocapsid antigen. Six individuals with confirmed COVID-19 and six individuals without COVID-19 are analyzed. Antibody titers in capillary venous whole blood did not show significant differences, and when corrected for hematocrit, they did not differ from the results obtained from serum. In conclusion, capillary sampled EDTA-anticoagulated whole blood seems to be an attractive alternative matrix for the evaluation of SARS-CoV-2 antibodies when employing ECLIA for detecting total antibodies directed against nucleocapsid antibodies.

Pan-immunoglobulin assays can simultaneously detect IgG, IgM and IgA directed against the receptor binding domain (RBD) of the S1 subunit of the spike protein (S) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 S1-RBD Ig). In this work, we aim to evaluate a quantitative SARS-CoV-2 S1-RBD Ig electrochemiluminescence immunoassay (ECLIA) regarding analytical, diagnostic, operational and clinical characteristics. Our work takes the form of a population-based study in the principality of Liechtenstein, including 125 cases with clinically well-described and laboratory confirmed SARS-CoV-2 infection and 1159 individuals without evidence of coronavirus disease 2019 (COVID-19). SARS-CoV-2 cases were tested for antibodies in sera taken with a median of 48 days (interquartile range, IQR, 43–52) and 139 days (IQR, 129–144) after symptom onset. Sera were also tested with other assays targeting antibodies against non-RBD-S1 and -S1/S2 epitopes. Sensitivity was 97.6% (95% confidence interval, CI, 93.2–99.1), whereas specificity was 99.8% (95% CI, 99.4–99.9). Antibody levels linearly decreased from hospitalized patients to symptomatic outpatients and SARS-CoV-2 infection without symptoms (p < 0.001). Among cases with SARS-CoV-2 infection, smokers had lower antibody levels than non-smokers (p = 0.04), and patients with fever had higher antibody levels than patients without fever (p = 0.001). Pan-SARS-CoV-2 S1-RBD Ig in SARS-CoV-2 infection cases significantly increased from first to second follow-up (p < 0.001). A substantial proportion of individuals without evidence of past SARS-CoV-2 infection displayed non-S1-RBD antibody reactivities (248/1159, i.e., 21.4%, 95% CI, 19.1–23.4). In conclusion, a quantitative SARS-CoV-2 S1-RBD Ig assay offers favorable and sustained assay characteristics allowing the determination of quantitative associations between clinical characteristics (e.g., disease severity, smoking or fever) and antibody levels. The assay could also help to identify individuals with antibodies of non-S1-RBD specificity with potential clinical cross-reactivity to SARS-CoV-2.

The vitamin B12 and folate status in nonanaemic healthy older persons needs attention the more so as decrease in levels may be anticipated from reduced haematinic provision and/or impaired intestinal uptake.

Abstract With increasing mean age of the world population it becomes clear that biological and chronological ages might diverge on individual levels. In contrast to working age adults, older people have a higher incidence of anemia mostly in association with medical comorbidities (Artz, Fergusson et al. 2004, Merchant and Roy 2012). Incidence of anemia in the elderly has so far been investigated in large studies mostly performed on hospitalized patients, nursing homes subjects or mobile examination centers subjects seeking medical care with a variety of complaints (Kikuchi, Inagaki et al. 2001, Guralnik, Eisenstaedt et al. 2004). In the USA, the 3rd NHANES study focused on racial groups of elderly revealing a prevalence of anemia in men and women >65 yrs of ∼10% (Izaks, Westendorp et al. 1999, Guralnik, Ershler et al. 2005). In patients over 85 yrs, this number exceeded 20%. Current reference intervals for clinical laboratory assays are based on younger adult's samples. Physiologic concentrations of hemoglobin (Hb) in human blood range from 120 g/l (female) and 130 g/l (male) to 168 g/l (both genders) under which anemia and above which polycythemia get diagnosed. We are currently in need for reference ranges suited for normal older subject and unbiased by already debilitated individuals. The defining cut-offs provided by the WHO are 120 g/l for women and 130 g/l for men (WHO Technical Report Series 1968); although older age is generally associated with lower Hb levels, these cut-offs do not account for age. We have performed a large recruitment as part of our Senior Labor study (Risch, Medina et al. 2012). In contrast to previous studies, we have prospectively recruited healthy Caucasian subjects over 60, implementing strong exclusion criteria for participating subjects. For those healthy individuals, a complete blood count (CBC) as well as frequently performed clinical laboratory tests were prospectively performed. A total of 1255 subjects consented to enroll for the study after having passed the primary clinical exclusion criteria which comprised one or more of the following questions affirmatively answered (primary exclusion criteria): drugs: do you take drugs containing steroids, are you under ill-adjusted antihypertensive therapy, do you suffer from thyroid diseases/are you substituted with thyroid hormones, do you have diabetes mellitus, have you suffered from cancer during the last 5 years, were you hospitalized during the month prior to enrolment and do you abuse alcohol. Complete blood count assays were done using an XE-5000 hematology analyzer and clinical chemistry assays followed routine workflow on modular platforms. We evaluated 696 women and 559 with ages ranging from 60 to 99 years old. Mean Hb and 95% confidence intervals were calculated using logarithmic transformation in order to correct of skewness of the data. Overall, women had a mean Hb of 136 (95%CI 120-155) and men had a mean Hb of 148 (95%CI 128-172). Detailed results by age groups are presented in figure 1. Hb level was steady over age groups until 74 yo for men and 79 for women. Interestingly, only a few subjects fell outside the WHO limits with 20 women having a Hb less than 120 (2.9%) and 20 men a Hb less than 130 (3.6%). We looked for frequent causes for anemia such as low ferritin and vitamin deficiencies (folic acid and B12). In the cohort, 37 subjects had a ferritin lower than 20 µg/l (2.9%). Among these, 9/37 (24.3%) had a low Hb (WHO definition) and only one in 37 (2.7%) had a MCHC below 310. The micronutrients folic acid and vitamin B12 were also assessed; 98 subjects (7.8%) had folic acid < 10 nmol/l. Among these individuals, 6/98 (6.1%) were anemic. The definition of vitamin B12 deficiency varies but is usually accepted as lower than 200 pmol/l in older persons: in the whole population, 398/1255 (31.7%) subjects had vitamin B12 levels < 200 pmol/L, and 105/1255 (8.4%) had vitamin B12 concentrations less than 150 pmol/L. Using these two limits, these subjects were anemic in 11/398 (2.8%) and 4/105 (3.8%) respectively. This indicates a limited impact of folic acid and B12 deficiency on anemia of the elderly. In this study, we were able to define new Hb reference range in older subjects reporting healthy by strict clinical criteria in a large cohort of subjects. Our results show a very limited proportion of subject with WHO defined anemia, thus indicating that even in older subjects, the discovery of a low Hb is likely to be associated to an underlying pathology. Disclosures: No relevant conflicts of interest to declare.